Method of printing a three-dimensional article

ABSTRACT

A three-dimensionally printed article comprises a build material and a support material, the support material comprising a hydroxypropyl methylcellulose having a DS of at least 1.0 and an MS of at least 0.6, wherein DS is the degree of substitution of methoxyl groups and MS is the molar substitution of hydroxypropoxyl groups. The support material can be removed from the build material by contacting the support material with water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.15/106,637 (now U.S. Pat. No. 10,259,921), filed Jun. 20, 2016, which isa U.S. National Phase Application of International Application No.PCT/US2015/010746, filed Jan. 9, 2015, which claims the benefit of U.S.Provisional Patent Application No. 61/928,015, filed Jan. 16, 2014, eachof which are hereby incorporated by reference in their entirety.

FIELD

The present invention relates to three-dimensionally printed articlesand a method of printing a three-dimensional article.

INTRODUCTION

Commercially available three-dimensional printers (3D), such as theProjet™ 3D Printers manufactured by 3D Systems of Rock Hill, S.C., use abuild material or ink that is jetted through a print head as a liquid toform various thermopolymer parts. Other printing systems are also usedto build 3D parts from material that is jetted through a printer head.In some instances, the build material is solid at ambient temperaturesand converts to liquid at elevated jetting temperatures. In otherinstances, the build material is liquid at ambient temperatures.Well-known build materials are poly(acrylonitrile-butadiene-styrene)(ABS) and polylactic acid (PLA).

Moreover, production of a three-dimensional part in a 3D printing systemoften requires the use of a support material in conjunction with thebuild material. E.g., the support material supports overhanging segmentsor portions which are not directly supported in the final geometry bythe build material. The support material can be used for several otherpurposes, e.g., to minimize warping from the build material's own load,to produce hollow sections, and/or to enable several moving componentsin the same part. The support material is also jetted through a printingnozzle as a liquid or extruded as a softened material and typicallyconsists of chemical species that are solid at ambient temperatures andfluid at elevated jetting temperatures. However, unlike the buildmaterial, the support material is subsequently removed after printing toprovide the finished three-dimensional part. The support material shouldbe removed without damaging the printed build material.

Removal of the support material can be administered through severalprocesses, including heating the support material to a temperature aboveits melting point in conjunction with the use of a suitable organiccarrier to sufficiently remove the support material from the buildmaterial. In some cases, the organic carrier deposits an undesirableoily residue on the completed three-dimensional part. Furthermore, theuse of elevated temperatures, in addition to a suitable organic carrier,in some situations can compromise the mechanical integrity of thefinished three-dimensional part resulting in part deformation orfailure.

To solve this problem, U.S. Pat. No. 5,503,785 suggests depositing arelease material as a thin coating between the build material and thesupport material. The release material is a hydrocarbon wax or awater-soluble wax, acrylates, polyethylene oxide, glycol-based polymers,polyvinyl pyrrolidone-based polymers, methyl vinyl ethers, maleicacid-based polymers, polyoxazolidone-based polymers, Polyquarternium IIor conventional mold release materials, such as fluorochemicals,silicones paraffins or polyethylenes. Depending on the type of releaselayer, it may also leave an undesirable oily residue on the completedthree-dimensional part. Moreover, the release layer adds complexity tothe three-dimensional printing of the articles.

A well-known support material is High Impact Polystyrene (HIPS). Afterthe 3D printing HIPS can be dissolved in limonene to remove HIPS fromthe printed build material. Unfortunately, limonene has a low flashpoint and leaves undesirable wastes.

Another known support material is polylactic acid (PLA). It can bedissolved in a heated sodium hydroxide solution. Unfortunately, PLAleaves undesirable wastes.

U.S. Pat. No. 6,070,107 discloses the use of poly(2-ethyl-2-oxazolidone)as water-soluble rapid prototyping support and mold material.Unfortunately, poly(2-ethyl-2-oxazolidone) is very tacky. Moreover, onthermal decomposition of poly(2-ethyl-2-oxazolidone) fumes aregenerated, specifically nitrogen oxides and carbon oxide, as disclosedin its Material Safety Data Sheet.

It is well known to use polyvinyl alcohol (PVA) as a support materialfor ABS. PVA and ABS can be printed simultaneously. After the 3Dprinting has been completed, the printed article can be submerged inwater. The PVA is dissolved in warm water and leaves the ABS portion ofthe printed article intact. Unfortunately, PVA is quite difficult toprint and does not sufficiently adhere to ABS. However, some adherenceof the support material to the build material is very desirable toprovide a good support and minimize warping of the build material.

In view of the deficiencies of the known support materials inthree-dimensional printing, one object of the present invention is toprovide another support material for three-dimensionally printedarticles.

A preferred object of the present invention is to provide a supportmaterial that is easily removable from the build material afterthree-dimensional printing of the support material and the buildmaterial. Another preferred object of the present invention is toprovide a support material that does not leave substantially toxic orcorrosive waste upon removal of the support material. Yet anotherpreferred object of the present invention is to provide a supportmaterial that has a reasonably good adhesion to the build material. Tofacilitate handling, yet another preferred object of the presentinvention is to provide a support material that has a low level ofsurface tackiness.

SUMMARY

Surprisingly, it has been found that certain hydroxypropylmethylcelluloses are very advantageous in three-dimensional printing.

Accordingly, one aspect of the present invention is athree-dimensionally printed article which comprises a build material anda support material, the support material comprising a hydroxypropylmethylcellulose having a DS of at least 1.0 and an MS of at least 0.6,wherein DS is the degree of substitution of methoxyl groups and MS isthe molar substitution of hydroxypropoxyl groups.

Another aspect of the present invention is a method of printing athree-dimensional article which comprises selectively depositing layersof a fluid build material to form the three-dimensional article on asubstrate; and supporting at least one of the layers of the buildmaterial with a support material, the support material comprising theabove-mentioned hydroxypropyl methylcellulose.

Yet another aspect of the present invention is the use of theabove-mentioned hydroxypropyl methylcellulose in three-dimensionalprinting.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A illustrates a three-dimensionally printed article that has beenprinted from one type of the hydroxypropyl methylcellulose supportmaterial.

FIG. 1B illustrates a three-dimensionally printed article that has beenprinted from another type of the hydroxypropyl methylcellulose supportmaterial.

FIG. 2 represents a picture, obtained by Scanning Electron Microscopy,of a portion of a three-dimensionally printed article at the interfaceof a hydroxypropyl methylcellulose support material and apoly(acrylonitrile-butadiene-styrene) build material.

FIG. 3 represents a picture, obtained by Scanning Electron Microscopy,of a portion of a three-dimensionally printed article at the interfaceof a hydroxypropyl methylcellulose support material and a polylacticacid build material.

DESCRIPTION OF EMBODIMENTS

The three-dimensionally printed article of the present inventioncomprises a build material and a support material. An essentialcomponent of the support material is the hydroxypropyl methylcellulosedescribed below. Surprisingly, this hydroxypropyl methylcellulose can besubjected to three-dimensional printing techniques and can be utilizedas or in a support material to support the build material of athree-dimensionally printed article. The hydroxypropyl methylcellulosecan be removed from the build material of the three-dimensionallyprinted article with the aid of water and leaves a non-toxic,non-corrosive and bio-degradable residue in the water.

The hydroxypropyl methylcellulose has a cellulose backbone having β-1,4glycosidically bound D-glucopyranose repeating units, designated asanhydroglucose units in the context of this invention. The degree of thesubstitution of hydroxyl groups of the anhydroglucose units by methoxylgroups and hydroxypropoxyl groups is essential in the present invention.The hydroxyl groups of the anhydroglucose units are not substituted byany groups other than methoxyl and hydroxypropoxyl groups.

The average number of methoxyl groups per anhydroglucose unit isdesignated as the degree of substitution of methoxyl groups, DS. In thedefinition of DS, the term “hydroxyl groups substituted by methoxylgroups” is to be construed within the present invention to include notonly methylated hydroxyl groups directly bound to the carbon atoms ofthe cellulose backbone, but also methylated hydroxyl groups ofhydroxypropoxyl substituents bound to the cellulose backbone.

The degree of the substitution of hydroxyl groups of the anhydroglucoseunits by hydroxypropoxyl groups is expressed by the molar substitutionof hydroxypropoxyl groups, the MS. The MS is the average number of molesof hydroxypropoxyl groups per anhydroglucose unit in the hydroxypropylmethylcellulose. It is to be understood that during thehydroxypropoxylation reaction the hydroxyl group of a hydroxypropoxylgroup bound to the cellulose backbone can be further etherified by amethylation agent and/or a hydroxypropoxylation agent. Multiplesubsequent hydroxypropoxylation reactions with respect to the samecarbon atom position of an anhydroglucose unit yields a side chain,wherein multiple hydroxypropoxyl groups are covalently bound to eachother by ether bonds, each side chain as a whole forming ahydroxypropoxyl substituent to the cellulose backbone. The term“hydroxypropoxyl groups” thus has to be interpreted in the context ofthe MS as referring to the hydroxypropoxyl groups as the constitutingunits of hydroxypropoxyl substituents, which either comprise a singlehydroxypropoxyl group or a side chain as outlined above, wherein two ormore hydroxypropoxyl units are covalently bound to each other by etherbonding. Within this definition it is not important whether the terminalhydroxyl group of a hydroxypropoxyl substituent is further methylated ornot; both methylated and non-methylated hydroxypropoxyl substituents areincluded for the determination of MS.

The hydroxypropyl methylcellulose utilized in the composition of thepresent invention has a DS of at least 1.0, preferably at least 1.4,more preferably at least 1.5, even more preferably at least 1.6, andmost preferably at least 1.7. The hydroxypropyl methylcellulosegenerally has a DS of up to 2.7, more typically up to 2.5, and even moretypically up to 2.4, and most typically up to 2.1.

The hydroxypropyl methylcellulose utilized in the composition of thepresent invention has an MS of at least 0.6, preferably at least 0.7,and more preferably at least 0.8. The hydroxypropyl methylcellulosegenerally has an MS of up to 1.9, typically up to 1.7, more typically upto 1.5, even more typically up to 1.3, and most typically up to 1.1.

The determination of the % methoxyl and % hydroxypropoxyl is carried outaccording to the United States Pharmacopeia (USP 35, “Hypromellose”,pages 3467-3469). The values obtained are % methoxyl and %hydroxypropoxyl. These are subsequently converted into degree ofsubstitution (DS) for methoxyl substituents and molar substitution (MS)for hydroxypropoxyl substituents. Residual amounts of salt are takeninto account in the conversion.

The hydroxypropyl methylcellulose utilized in the composition of thepresent invention preferably has a viscosity of up to 100 mPa·s, morepreferably up to 60 mPa·s, even more preferably up to 40 mPa·s, and mostpreferably up to 30 mPa·s, or up to 20 mPa·s, or up to 10 mPa·s,determined as a 2% by weight solution in water at 20° C. in a HaakeVT550 Viscotester at a shear rate of 2.55 s⁻¹. The viscosity ispreferably at least 1.2 mPa·s, and more preferably at least 2.4 mPa·s orat least 3 mPa·s. Hydroxypropyl methylcelluloses of such viscosity canbe obtained by subjecting a hydroxypropyl methylcellulose of higherviscosity to a partial depolymerization process. Partialdepolymerization processes are well known in the art and described, forexample, in European Patent Applications EP 1,141,029; EP 210,917; EP1,423,433; and U.S. Pat. No. 4,316,982.

The hydroxypropyl methylcelluloses utilized in the present invention andtheir use as thickening agents for organic liquids are described in U.S.Pat. No. 4,614,545, but their utility in three-dimensional printing hasbeen unknown before the present invention. The composition of thepresent invention can comprise one or more of the above-describedhydroxypropyl methylcelluloses.

The support material preferably does not comprise more than 5 weightpercent, more preferably not more than 3 weight percent, and mostpreferably not more than 1 weight percent of water, based on the totalweight of the support material. Moreover, the support materialpreferably does not comprise more than 5 weight percent, more preferablynot more than 3 weight percent, and even more preferably not more than 1weight percent of an organic solvent having a boiling point of up to230° C. at atmospheric pressure, based on the total weight of thesupport material. Most preferably the support material does not comprisewater or an organic solvent having a boiling point of up to 230° C. atatmospheric pressure.

The support material may further comprise additives, different from theabove-mentioned hydroxypropyl methylcellulose, such as rheologicalmodifiers, stabilizers, fillers, plasticizers, pigments and/or impactmodifiers. However, an advantage of the present invention is that thepresence of such additives different from the above-mentionedhydroxypropyl methylcellulose is optional. The support material does notrequire the content of a substantial amount or any amount of suchadditives. More specifically, the support material does not require thepresence of a substantial amount or any amount of waxes, oils orlubricants which might leave an oily or waxy surface of the buildmaterial after removal of the support material.

Non-limiting examples of fillers are carhohydrates, sugars, sugaralcohols, proteins, or NaCl. Non-limiting examples of surfactants thatcan be used in the practice of the present invention are C₈ to C₂₂ fattyacids and/or their derivatives. Additional surfactant components thatcan be used with these fatty acids are C₈ to C₂₂ fatty esters, C₈ to C₂₂fatty alcohols, and combinations of these. Exemplary surfactants arestearic, lauric, oleic, linoleic, palmitoleic acids, and theirderivatives, stearic acid in combination with ammonium lauryl sulfate,and combinations of all of these. Most preferred surfactants are lauricacid, stearic acid, oleic acid, and combinations of these. The amount ofsurfactants typically may be from 0.1 to 3 percent, based on the weightof the hydroxypropyl methylcellulose. Non-limiting examples oflubricants are for example polyethylene oxide homopolymers, copolymersand terpolymers, glycols, or oil lubricants, such as light mineral oil,corn oil, high molecular weight polybutenes, polyol esters, a blend oflight mineral oil and wax emulsion, a blend of paraffin wax in corn oil,and combinations of these. Typically, the amount of oil lubricants isfrom 0.1 to 10 percent, more typically from 0.3 to 6 percent, based onthe weight of the hydroxypropyl methylcellulose.

Uniform mixing of the hydroxypropyl methylcellulose with one or moreoptional additives, e.g., selected from surfactants, lubricants,stabilizers and antioxidants to produce the support material can beaccomplished by, for example, a known conventional kneading process.

The above-described hydroxypropyl methylcellulose generally amounts toat least 50 wt %, preferably at least 60 wt %, more preferably at least70 wt %, and even more preferably at least 90 wt %, based on the totalweight of the support material. The amount of the hydroxypropylmethylcellulose is up to 100 wt %, and preferably up to 95 wt %, basedon the total weight of the support material.

One aspect of the present invention is the use of a hydroxypropylmethylcellulose disclosed further above in three-dimensional printing,preferably the use of the hydroxypropyl methylcellulose as a supportmaterial for at least one layer of a build material.

Known build materials are e.g., thermoplastic polymers, such aspolyoxymethylene, polylactic acid, ethylene vinyl acetate copolymers,polyphenylene ether, ethylene-acrylic acid copolymer, polyether blockamide, polyvinylidene fluoride, polyetherketone, polybutyleneterephthalate, polyethylene terephthalate, polycyclohexylenemethyleneterephthalate, polyphenylene sulfide, polythalamide,polymethylmethacrylate, polysulfones, polyethersulfones,polyphenylsulfones, polyacrylonitrile,poly(acrylonitrile-butadiene-styrene), polyamides, polystyrene,polyolefin, polyvinyl butyral, polycarbonate, polyvinyl chloridespolyurethanes, polyethylenes, polypropylenes, and combinations, thereof.Preferred build materials are those known for fused deposition modeling(FDM) techniques, such as a poly(acrylonitrile-butadiene-styrene), apolycarbonate, or polylactic acid.

Another aspect of the present invention is a method of printing athree-dimensional article which comprises: selectively depositing layersof a fluid build material to form the three-dimensional article on asubstrate; and supporting at least one of the layers of the buildmaterial with a support material, the support material comprising theabove-described hydroxypropyl methylcellulose and optional additives asdescribed above. Suitable substrates on which the three-dimensionalarticle is formed are known in the art, such as plates or sheets made ofglass, metal or synthetic materials.

The method of the present invention is preferably carried out accordingto fused deposition modeling (FDM) or according to selective depositionmodeling (SDM), wherein two different polymers are melted in nozzles andselectively printed, one being a build material and the other one beingthe support material. The build material and the support material can beheated to the same or different temperatures to bring them into a moltenor softened shape. The support material that comprises, substantiallyconsists of or even consists of the above-mentioned hydroxypropylmethylcellulose is typically heated to a temperature of at least 100°C., preferably at least 110° C. The temperature should generally not beabove the temperature where the hydroxypropyl methylcellulose begins todegrade. Generally the support material is heated to a temperature of upto 230° C., preferably up to 220° C., and more preferably up to 200° C.Typically the build material is also heated to a temperature of at least100° C., or at least 110° C., and up to 230° C., or up to 220° C., or upto 200° C. The FDM process is described in U.S. Pat. No. 5,121,329, theteaching of which is incorporated herein by reference. Typically thebuild material and/or support material, is selectively depositedaccording to an image of the three-dimensional article, the image beingin a computer readable format. For example, the build material can bedeposited according to preselected computer aided design (CAD)parameters. In some embodiments of the invention the fluid buildmaterial solidifies upon deposition. In other embodiments the buildmaterial, comprises a curable material, such as a or more photo-curablechemical species.

In the method of the present invention the support material comprises,substantially consists of, or consists of the above-describedhydroxypropyl methylcellulose. At least one of the layers of the buildmaterial is supported with the support material. The support material isonly temporarily needed. Upon hardening of the build material, e.g., bycooling, the support material is removed. For example, the hydroxypropylmethylcellulose is removed in a washing step wherein the hydroxypropylmethylcellulose dissolves in water, preferably in water of ambienttemperature, leaving the build material behind that forms the actualdesired three-dimensional object. For example, the entirethree-dimensionally printed article comprising the build material andthe support material is placed in a water bath or is contacted withrunning water so that the water dissolves the hydroxypropylmethylcellulose and leaves the desired three-dimensional object producedfrom the build material behind. It is a great advantage of the presentinvention that the hydroxypropyl methylcellulose utilized as supportmaterial or as an essential component of the support material can beremoved from the build material by simply contacting the supportmaterial with water. The hydroxypropyl methylcellulose leaves non-toxicwastes. Moreover, at least in the preferred embodiments of theinvention, the hydroxypropyl methylcellulose can be removed faster thansupport materials known in the prior art.

Some embodiments of the invention will now be described in detail in thefollowing Examples.

EXAMPLES

Unless otherwise mentioned, all parts and percentages are by weight. Inthe Examples the following test procedures are used.

Examples 1 and 2 Preparation of Filaments for Three-Dimensional (3-D)Printing

Filaments for three-dimensional printing are produced from two differenthydroxypropyl methylcellulose (HPMC) powder samples having a DS(methyl), a MS(hydroxypropoxyl) and a viscosity as listed in Table 1below. The HPMC samples are prepared using a known method foretherification of alkalized cellulose. The etherification agents methylchloride and propylene oxide are added to alkali cellulose and reactedat elevated temperatures. The resulting crude HPMC is neutralized,washed free of chloride using hot water, dried and ground. The producedHPMC is subjected to partial depolymerization by heating the HPMC powderwith gaseous hydrogen chloride at a temperature of 60-85° C. for 80-100min.

The determination of the % methoxyl and % hydroxypropoxyl is carried outaccording to the United States Pharmacopeia (USP 35, “Hypromellose”,pages 3467-3469). These are subsequently converted into degree ofsubstitution (DS) for methoxyl substituents and molar substitution (MS)for hydroxypropoxyl substituents. The viscosity of the HPMC samples isdetermined as a 2% by weight solution in water at 20° C. in a HaakeVT550 Viscotester at a shear rate of 2.55 s⁻¹.

TABLE 1 2% Viscosity in water HPMC DS (methyl) MS(hydroxypropoxyl) at20° C. (mPa · s) HPMC-1 2.2 1.2 40 HPMC-2 1.9 0.9 5

A capillary rheometer (Malvern RH10, Malvern Instruments) equipped witha die which is suitable to produce HPMC filaments of 1.8 mm is heated upto 175° C. in the case of HPMC-1 or 145° C. in the case of HPMC-2 andfilled with the HPMC powder. The vertical extrusion through the die isperformed with a piston driving at about 5 mm/min. The resultingspaghetti-like filaments of 1.8 mm diameter are hardened by cooling toroom temperature. They are subsequently used for the 3-D-printing stepwithout any further treatment.

3-D Printing of HPMC Filaments

A 3D Printer MakerBot Replicator 2X, which is commercially availablefrom Stratasys Ltd, Minneapolis, Minn. (USA), is used for 3-D printing.

FIG. 1A illustrates an article that has been three-dimensionally printedat 200° C. from the HPMC-1 filaments of 1.8 mm.

FIG. 1B illustrates an article that has been three-dimensionally printedat 210° C. from the HPMC-2 filaments of 1.8 mm.

Printing trials are repeated several times with HPMC-1 and HPMC-2wherein the 3D Printer is heated to different temperatures in the rangeof 180 to 230° C. All HPMC samples display good 3-D printability. TheHPMC filaments can be easily loaded into the printer nozzle. All HPMCsamples display good bonding between the individual layers of the HPMCmaterial.

Solubility in Water

Filaments having a diameter of 1.8 mm are produced from HPMC-1 andHPMC-2 in the capillary rheometer as described above.

For comparative purposes a polyvinyl alcohol (PVA) filament having adiameter of 1.8 mm is evaluated. The polyvinyl alcohol filament iscommercially available from Stratasys Ltd, Minneapolis, Minn. (USA).Polyvinyl alcohol is a known support material for three-dimensionalprinting which is considered as the material which is easiest andfastest to remove after three-dimensional printing.

Samples of the filaments produced from PVA, HPMC-1 and HPMC-2, allhaving a diameter of 1.8 mm, the same length and a temperature of 20°C., are placed into jars, each equipped with a shaker and containingwater of a temperature of 20° C. The filaments are placed on the shakerthat has been placed into the water. The dissolution of the filaments ismonitored as the function of time. Weight measurements of the remainingfilaments are carried out and listed in Table 2 below as percentage ofthe original weight. A weight over 100% is due to water uptake by thefilaments when they swell in water.

TABLE 2 Wt % of filament, based on weight at time = 0 min. HPMC-1 HPMC-2PVA (Comp.) at 0 min 100.0% 100.0% 100.0% at 10 min 100.0%  72.5% 102.0%at 20 min 100.0%  28.7% 102.4% at 25 min 100.0%  6.7% 101.7% at 30 min100.0%  0.9% 110.2% at 35 min 100.0%  0.0% 101.1% at 60 min 101.9% —101.0% at 120 min 103.5% — 101.1%

As it can be seen from the results in Table 2, HPMC-1 and PVA showsimilar behavior with some swelling and weight gain. This swelling andsoftening occurs faster in PVA than in HPMC-1. The results in Table 2illustrate that a hydroxypropyl methylcellulose having a DS of at least1.0 and an MS of at least 0.6 is as useful as a support material forthree-dimensional printing as polyvinyl alcohol (PVA) which is widelyused for this purpose.

The weight of HPMC-2 reduces very quickly from the beginning. Thethickness of the filament produced from HPMC-2 is visibly reduced; in 35minutes of soaking in water the filament has completely disappeared.Since cleaning operation after 3-D printing often takes longer thanprinting itself, HPMC-2, which represents a preferred embodiment of theinvention, shows a great advantage. Not only it is non-toxic and can beremoved by washing just in water, but it can also be removed in muchshorter time than PVA.

Examples 3-9 and Comparative Examples A-C Extrusion Trials

Samples of HPMCs are provided which have a DS (methyl), a MS(hydroxypropoxyl) and a viscosity as listed in Table 3 below. Thesamples are prepared as described for Examples 1 and 2 above.

A 30 ml kneading cell W30 of a Brabender Plasti-Corder PL 2000 torquekneader with a metallic cover is heated to a temperature above thesoftening temperature of the HPMC, as listed in Table 3 below. Afterautomatic calibration of the empty cell, HPMC powder is filled into thecell. Homogenization is carried out at 30 rpm until a constant torque isreached.

A capillary rheometer (Malvern RII10, Malvern Instruments) having a dieof 1.7 mm diameter and 27.2 mm length is heated to the temperaturelisted in Table 3 below and filled with a paste coming out of the torquekneader. Vertical extrusion through the die is performed with a pistonmoving at about 5 mm/min. The resulting spaghetti-like filaments areevaluated by visual inspection.

As illustrated by the results in Table 3, HPMCs which do not have an MSof at least 0.6 do not have sufficient thermoplasticity to be useful inthree-dimensional printing.

TABLE 3 HPMC properties Extrusion 2% softening Kneading Extrusion temp.viscosity Temp. Temp. Result (° C.)/pressure HPMC DS MS (mPa · s) (° C.)(¹) (° C.) (²) (³) (MPa) HPMC-3 2.00 0.76 7 109 118 Plastic 123° C./9MPa  HPMC-4 2.05 0.80 14 100 102 Plastic 170° C./11 MPa HPMC-5 2.02 0.836 100 148 Plastic 120° C./1 MPa  HPMC-6 1.97 0.80 6 98 101-110 Plastic120° C./3 MPa  HPMC-7 1.90 0.93 6 132 157-167 Plastic 165° C./n.d.HPMC-8 1.91 1.04 7 137 156 Plastic 165° C./13 MPa HPMC-9 1.84 1.17 5 133148 Plastic 170° C./11 MPa HPMC-A 1.49 0.15 180 >240 Not — (⁴) Notpossible (Comp.) possible HPMC-B 1.81 0.18 50 >240 Not — (⁴) Notpossible (Comp.) possible HPMC-C 1.92 0.44 4300 >240 Not — (⁴) Notpossible (Comp.) possible (¹) softening temperature, determined with ahot stage microscope, heating rate: 2° C./min. (²) real temperature inthe kneading cell before kneading start (³) paste properties in thekneader after visual inspection n.d.: not determined (⁴) Particles donot melt, no plastic mass

Example 10 Three-Dimensionally Printed ABS Article

A three-dimensional article is produced from a HPMC-1 filament of 1.8 mmas the support material and a poly(acrylonitrile-butadiene-styrene)(ABS) filament of 1.8 mm diameter as the build material. The ABSfilament are commercially available from Stratasys Ltd, Minneapolis,Minn. (USA).

A 3D Printer MakerBot Replicator 2X, which is commercially availablefrom Stratasys Ltd, Minneapolis, Minn. (USA), is used for 3-D printing.HPMC-1 and ABS are printed from two printing nozzles at 230° C.

FIG. 2 represents a picture, obtained by Scanning Electron Microscopy(SEM), of a portion of the three-dimensionally printed article at theinterface of the HPMC-1 support material and the ABS build material. TheSEM picture shows no delamination at the interface, which is anindication of a good adhesion between the printed HPMC-1 supportmaterial and the ABS build material.

Example 11 Three-Dimensionally Printed ABS Article

Example 10 is repeated, except that a HPMC-2 filament of 1.8 mm is usedas the support material. A good adhesion between the printed HPMC-2support material and the ABS build material is achieved.

Example 12 Three-Dimensionally Printed PLA Article

Example 10 is repeated, except that polylactic acid (PLA) is used as abuild material. The PLA filaments of 1.8 mm diameter are commerciallyavailable from Stratasys Ltd, Minneapolis, Minn. (USA). The same 3DPrinter as in Example 10 is used for 3-D printing. HPMC-1 and PLA areprinted from 2 printing nozzles at 215° C. Inspection of the interfacesshows no delamination, indicating good interfacial bonding.

Printing at lower temperature (180° C.) results in weaker adhesionbetween PLA and HPMC-1 and delamines easier after cooling.

Example 13 Three-Dimensionally Printed PLA Article

Example 12 is repeated, except that a HPMC-2 filament of 1.8 mm is usedas the support material. Essentially the same results are obtained as inExample 12.

The invention claimed is:
 1. A method of printing a three-dimensionalarticle comprising: selectively depositing layers of a fluid buildmaterial to form the three-dimensional article on a substrate; andsupporting at least one of the layers of the build material with asupport material, the support material comprising a hydroxypropylmethylcellulose having a DS of at least 1.0 and an MS of at least 0.6,wherein DS is the degree of substitution of methoxyl groups and MS isthe molar substitution of hydroxypropoxyl groups, and at most 5 weightpercent of water.
 2. The method of claim 1, wherein the layers of thebuild material are deposited according to an image of thethree-dimensional article in a computer readable format.
 3. The methodof claim 2 further comprising hardening the build material.
 4. Themethod of claim 3 further comprising removing the support material fromthe build material by contacting the support material with water.
 5. Themethod of claim 1 wherein the amount of the hydroxypropylmethylcellulose is at least 50 weight percent of the total weight of thesupport material.
 6. The method of claim 1 wherein the hydroxypropylmethylcellulose has a DS of at least 1.4.
 7. The method of claim 1wherein the hydroxypropyl methylcellulose has a DS of from 1.6 to 2.5.8. The method of claim 1 wherein the hydroxypropyl methylcellulose hasan MS of from 0.6 to 1.7.
 9. The method of claim 1 wherein the buildmaterial comprises a thermoplastic material selected from the groupconsisting of poly(acrylonitrile-butadiene-styrene), polycarbonate,polylactic acid and polyethylene terephthalate.
 10. The method of claim1 wherein the hydroxypropyl methylcellulose has a viscosity that is upto 30 mPa·s, determined as a 2% by weight solution in water at 20° C.11. The method of claim 1 wherein both the build material and thesupport material are melted in nozzle and selectively printed.
 12. Themethod of claim 11 wherein the hydroxypropyl methylcellulose has an MSof from 0.7 to 1.3.
 13. The method of claim 1 wherein the supportmaterial has at most 3 weight percent of water.
 14. The method of claim1 wherein the support material has at most 1 weight percent of water.